Analytical expressions for radiatively corrected Higgs masses and couplings in the MSSM

We propose, for the computation of the Higgs mass spectrum and couplings, a renormalization-group improved leading-log approximation, where the renormalization scale is fixed to the top-quark pole mass. For the case m_A\sim M_{\rm SUSY}, our leading-log approximation differs by less than 2 GeV from previous results on the Higgs mass computed using a nearly scale independent renormalization-group improved effective potential up to next-to-leading order. Moreover, for the general case m_A\simlt M_{\rm SUSY}, we provide analytical formulae (including two-loop leading-log corrections) for all the masses and couplings in the Higgs sector. For M_{\rm SUSY}\simlt 1.5 TeV and arbitrary values of m_A, \tan\beta and the stop mixing parameters, they reproduce the numerical renormalization-group improved result for the Higgs masses with an error of less than 3 GeV. For the Higgs couplings, our analytical formulae reproduce the numerical results equally well. Comparison with other methods is also performed.